Hydraulic brake



P. N. WILSON 2,670,815

3 Sheets-Sheet 1' 5 Inventor .2 MHL LEO-Z21 HYDRAULIC BRAKE I III March2, 1954 Filed Feb. 20, 1950 Filed Feb. 20, 1-950 3 Sheets-Sheet 2-P.1YffzLlsoru March 2, 1954 p, w Lso r 2,670,815

HYDRAULIC BRAKE Filed Feb. 20, 1950 3 Sheets-Sheet 3 are described indetail below.

Patented Mar. 2, 1954 HYDRAULIC BRAKE Paul Norman Wilson,v Kendal,England, asslgnor to Gilbert Gilkes & Gordon Limited, Kendal,-

England Application February 20, 1950,: Serial, No. 145,108

2 Claims. (01. 188:--90) This invention relates to hydraulic brakes forabsorbing power generated by a prime mover and more especially anhydraulic turbine generating power.

In British specification N0. 22,909/47, there is described a plantincorporating an hydraulic brake which in effect is a Pelton wheel, therotor of which is caused to rotate in opposition to a jet of liquidadmitted to the casing in which the rotor is enclosed.

An hydraulic turbine of this type usedas a brake should have thecharacteristic that when it is absorbing power it shall absorb themaximumamount of power with the minimum supply of water or other liquidimpinging on the rotor whilst when running free it should be soconstructed that windage or other frictional losses are reduced.

The object of the present invention is to provide an hydraulic brake,the rotor of which in effect isa Pelton Wheel rotated in opposition tothe jet of liquid introduced into its casing.

One feature of the invention consists in forming the rotor so that itsopposite sides adjacent to its periphery conform with the surface of theside walls of the casing.

Further, and in some instances optional features and the purposes theyare designed to serve In order that the maximum power may be absorbedthe velocity of the rotor at the radius at which the jet strikes thebuckets with which it is provided or formed must be maintained at thehighest possible figure.

The mechanical strength of the rotor must therefore be great and tosecure this result most satisfactorily the buckets or vanes are formedin the rim of the rotor and between the side walls of the rim and areprovided with means allowing the braking liquid to escape through ventsformed onv each side of the rotor.

ThuS the rotor may be a casting or forging. in whichv the buckets areintegrally formed.

In order that frictional losses may be reduced to a minimum when therotor is rotating freely and no braking effect is required, the sidewalls of the casing ar pr f rably ymmetrical as with an unsymmetricalcasing similar to that employed to shield a Pel'ton wheel or similarfree jet impulse turbine in which the. water falls away in the, lowerportion of the casing, violent air snrges are set up causingrelativelyllishi power absorption when the rotor revolves whether or nota braking effect is desired.

The buckets or vanes are formed in the rim of the rotor in such mannerthat they are concave when viewed along the axis of the entering jet orjets of liquid which strike against them to produce the braking effectand at this point it may be repeated that the rotor rotates towards thejet and not away'fro-m it'as inthe case of the conventional free jetimpulseturbine of the Pelton or similar type. r v

7 Owing to the shape of the buckets or vanes in the rotor of anhydraulic brake in accordance with the invention, the dischargevelocityof the liquid is increased and may be several times the velocity of theentering liquid.

By this means a relatively small amount of liquid may be used to absorbarelatively large amount of power in thebrake.

Conveniently the'supply of liquid by way of the jet is controlled by theprovision of a variable spear controlled noz zle valve and supply pipe.

This spear control may be operated by "hand. or by a speed governor;

Alternatively; a fixedsize nozzle may be substituted; a valve beingprovided in the supply line for operation by hand or by a speedgovernor.

In certain cases instead of varying the rate at which liquid enters therotor chamber by the operation of a valve, a nozzle adapted to give afixed supply of liquid may be used and a deflector introduced betweenthe nozzle and the rotor to vary the volume of braking liquid strikingthe buckets in the rotor,

Alternatively, both a, variable spear control valve and a deflectorcontrol maybe provided.

In order to prevent air entering or liquid leaving the casing along theshafts, a labyrinth or thrower system or alternatively a gland systemmay be arranged where the shaft passes through the walls of the chamberin which the rotor revolves. I

The invention will be described further in detail and by way of examplewith reference to the accompanying drawings in which:

i re 1: a view in sectional elevation of a hydraulic brake in accordancewith the invention";

Figure 2- is a planview thereof with the upper half of the casingremoved;

Figure 3 is a diagrammatic representation illustrating the applicationof the braking mecha nism in connection with a water turbine drivenelectric, generator.

As will be seen fromthe drawings, the rotor I istorm'zd to provide.opposite faces 2 which con form with the surface of the sidewalls 3 ofthe" casing.

The mechanical strength of the rotor must be great and to secure thisresult the buckets or vanes 4 are formed on the rim 5 of the rotor whichpreferably is a casting or forging.

The side walls of the rim are provided with vents 6 formed on each sideof the rotor to allow the braking liquid to escape from the buckets.

It will be noted that the casing in which the rotor rotates issymmetrical with the rotor in order that air surges shall not be set upcausing a relatively high power of absorption when the rotor revolves,whether or not a braking effect is desired. a

The buckets, as will be seen, are concave along the axis of the entryjet I.

In the construction shown the jet is variable by the provision of avalve furnished with a spearhead control member 8 which is urged towardsa nozzle 9 by a spring l0 engaged between a plate H and an abutmentmember 12, the stem [3 of the valve being furnished with an eye I4 forcon.- necting it with the mechanism which will be described generallywith reference to Figure 3.

. As shown in Figure 1, the lower half of the rotor is substantiallysurrounded by a line 15 in which is provided an aperture [6 throughwhich the braking liquid may escape and enter a deflector I1.

The rotor shaft 18 is preferably furnished with a labyrinth or glandpacking, not shown, in order to prevent air entering or liquid leavingthe casing along the shaft.

As above indicated, the braking device is designed more particularly tobe included in a plant as described in British specification No.22,909/47 and such application of the device is illustrated purelydiagrammatically in Figure 3 in which 20 is an hydraulic turbine of theFrancis type in the lead 2! to which is included a valve 22 which willnormally be agate valve connected with a governor 23 which is drivenfrom the shaft 24 on which the rotor of the turbine is mounted and whichis connected to the shaft of the armature of a generator 25 which inturn is connected with the shaft 26 of the hydraulic brake 21 to whichis by-passed a portion of the liquid supplied by way of the pipe 28through a nozzle 29 in which operates a spearhead valve connectedthrough a bell crank lever and link 30 with the cylinder of a dashpotdevice 3| the pistonof which is connected by a system of links 32 withthe governor.

It is therefore clear that the present invention provides a hydraulicbrake mechanism that comprises a cylindrical casing having symmetricalfacing side walls 3. The shaft to be braked is journalled for rotationin the casing and carries a rotor body. This shaft rotates at a highspeed in a predetermined direction. The rotor body has oppositesymmetrical side walls 2 conforming in symmetry to the facing side wallsof the casing. The rotor body is of less diameter than the internaldiameter of the casing and has less axial extent than the distancebetween the facing side walls of the casing so that space exists betweenall surfaces of the rotor body and the casing. Means are associated withthe casing for directing at least one jet of liquid such as water,tangentially into the casing through the periphery thereof and in adirection opposite to the direction of rotation of the rotor. Ashereinbefore set forth, the rotor body has its periphery shaped todefine recessed buckets or vanes 4 that are located between the sidewalls of the rotor. The peripheral surfaces of these vanes are concavein a 4 circumferential direction as viewed along the axis of the jet.This presents arcuate surfaces to be impinged upon by the jet as therotor rotates. The outlet l6 has its axis perpendicular to the axis ofthe jet and on the side of the axis of the jet opposite to the axis ofthe rotor so that the discharge velocity of liquid is increased and a'high relative velocity exists between the rotor periphery and the jet.This provides for a high power absorption at minimum liquid supply. Aspreviously pointed out in the specification, the symmetrical arrangementof rotor and easing side walls minimize air surges within the casing.The side walls of the rotor body have liquid egress openings thereinthat provide communication between the buckets and the space between therotor and casingsidewalls to allow braking liquid to vent or passthrough these openings.

I claim:

1. A hydraulic brake mechanism comprising a cylindrical casing havingsymmetrical facing side walls, a rotor body journalled for rotation inthe casing and adapted to rotate at a high speed in a predetermineddirection, said rotor body having opposite symmetrical side wallsconforming in symmetry to the facing side walls of the casing and havingless diameter than the internal diameter of the casing, said rotor bodyfurther having less axial extent than the distance between the facingside walls of the casing so that space exists between all surfaces ofthe rotor and the casing, means for directing at least one jet ofliquid, tangentially into the casing through the periphery thereof andin a direction opposite to the direction of rotation of the rotor, saidrotor body having its periphery shaped to define recessed bucketsconstituting vanes located between the side walls of the rotor, theperipheral surfaces of the vanes being concave in a circumferentialdirection as viewed along the axis of the jet so as to present arcuatesurfaces to be impinged upon by the jet as the rotor rotates, theperiphery of the casing having an outlet opening therein, the axis ofwhich is perpendicular to the axis of the jet and on the side of theaxis of the jet opposite to the axis of the rotor body so that thedischarge velocity of liquid is increased and a high relative velocityexists between the rotor periphery and the jet in order to provide forhigh power absorption at minimum liquid supply and the symmetricalarrangement of rotor and easing side walls minimizing air surges withinthe casing.

2. A hydraulic brake as defined in and by claim 1, in which the sidewalls of the rotor body have liquid egress openings therein providingcommunication between the buckets and the space between the rotor andcasing side walls.

PAUL NORMAN WILSON.

References Cited in the file of this patent UNITED STATES PATENTSSwitzerlandu" Dec. 1, 1930

